One can research and view articles, book and videos of Gurus all through the internet and choose the root Guru depending on who impact you the most. One much take the time to "select" as in the 50 Stanzas of Guru Devotion. Once decided we can make offerings and prayer; assuming one cannot meet the Guru physically, then in front of the Guru's photo and generate the request that one has taken that Guru and the root Guru. Then, everyday do the Guru Yoga prayers or whatever Guru prayers that the Guru's lineage and hence your lineage everyday and practice the Dharma according to the lineage.
Hence, it is important that one much research well and the decision must be made based also on the availability of the Guru's lineage practice. Also, one can try to contact the Guru for this and on taking refuge with him.
On initiations, I do not think it is possible without taking it directly with a Tantric who can be the Guru or any others that the Guru prescribes.
But taking refuge is possible and a must for any other practices to be given and effective practiced.